4 th Esri Eastern Africa Education GIS User Conference Geospatial Technology Based Regolith Mapping in the Western Metamorphic Terrain, Ethiopia. BY: Gizachew Kabite Date: 23/2016
Presentation outlines Introduction Methods and Materials Description of the Study Area Methodology followed Results and Discussions Conclusions 9/30/2016 Regolith Mapping 2
Introduction Regolith: all weathering products accumulated on basement rocks overtime (Crooks, 2002). Includes both in-situ weathered and transported. Regolith map can be used for several applications (Roach, 2003). Remote sensing can provide valuable information for regolith mapping and characterization (Kruse et al., 2003; Perry, 2004). Band ratio and Principal Component Analysis are the common image analysis used for information extraction (Yesou et al., 1993). Scarcely utilized for regolith mapping. Processed Landsat shows high degree of regolith-landform map. 9/30/2016 Regolith Mapping 3
Introduction Despite the valuable application of regolith mapping, very few research were done so far globally but even no research were tried in Ethiopia. Objective of the Study To map and characterize regolith in the study area using the state-of-the-art so as to provide baseline information particularly for groundwater potential and mineral exploration studies. 9/30/2016 Regolith Mapping 4
Materials and Methods Description of the Study Area 35°0'0"E 40°0'0"E 45°0'0"E Western Metamorphic Terrain is one 15°0'0"N Eritrea 15°0'0"N Yemen of the largest basement terrain in · Sudan Ethiopia. Djibouti Red Sea Covers about 85,000km 2 total area. 10°0'0"N 10°0'0"N The area is endowed mainly with Ethioipia gold and marble mineral resources. Legend International Boundary Study Area South Sudan 5°0'0"N 5°0'0"N Somalia Kenya Uganda Indian Ocean 35°0'0"E 40°0'0"E 45°0'0"E 1:8,000,000 Kms 0 90 180 360 540 720 9/30/2016 Regolith Mapping 5
Materials and Methods Methodology ASTER DEM (30*30m) ETM+ Images Pre-processing Pre-Processing 5/7, 5/4, DPCA, 5/4, 7, 5, 1 3/1 7+1 Elevation class Slope Class Comparison of the images Landform unsupervised Classification Overlay Analysis Classified Regolith classes Regolith Land Units Map DPCA(4/3 & 5/7) separate clay from vegetation; 5/4 highlights ferruginous materials; 7+1 highlight silicate-rich materials; 5/7 indicate clay mineral and 3/1 indicate Iron-oxide. 9/30/2016 Regolith Mapping 6
Results and Discussions Clay Minerals 35°0'0"E 36°0'0"E 37°0'0"E Mapped from 5/7 band ratio (Richards & Xiuping, · 12°0'0"N 2006). Used to identify hydroxyl-bearing minerals 11°0'0"N High value indicates the presence of clay minerals while low value shows unaltered rocks (Rawashdeh 10°0'0"N et al., 2006). Legend 9°0'0"N The spatial variation of clay content in the area Clay Mineral Value High : 24.6 revealed diversity of weathering intensity. Low : 0 The high value indicates active weathered area. 8°0'0"N Lower value revealed areas with relatively unaltered rocks. 7°0'0"N 1:2,600,000 Kms 0 15 30 60 90 120 9/30/2016 Regolith Mapping 7
Results and Discussions Iron-Oxide 35°0'0"E 36°0'0"E 37°0'0"E Recognized using ratio of band 3/1 (Druy, 1993; Richards · 12°0'0"N and Xiuping, 2006). High value indicates the presence of weathered iron 11°0'0"N minerals while non-iron-oxide bearing zones (Rawashdeh et al., 2006). 10°0'0"N Iron-oxide varies spatially within the study area revealing variation of weathering extent in the areas. 9°0'0"N Legend Iron Oxide High : 2.3 Area with high clay content are shown to have low Iron- Low : 0 8°0'0"N oxide. 7°0'0"N 1:2,600,000 Kms 0 15 30 60 90 120 9/30/2016 Regolith Mapping 8
Results and Discussions Ferrous Mineral 35°0'0"E 36°0'0"E 37°0'0"E Band · ratio of 5/4 is used to identify ferrous 12°0'0"N mineral((Papp, 2002). High value corresponds to high ferrous mineral while 11°0'0"N low value indicates the presence of non-ferrous mineral. The spatial distribution of Ferrous minerals also 10°0'0"N indicates the variation of weathering extent in the area. 9°0'0"N Area with high clay mineral also contain low ferrous Legend Ferrous Mineral High : 24 minerals. Low : 0 8°0'0"N 7°0'0"N 1:2,600,000 Kms 0 15 30 60 90 120 9/30/2016 Regolith Mapping 9
Results and Discussions Regolith Units 35°0'0"E 36°0'0"E 37°0'0"E · Classified from color composite of DPCA band ratio 12°0'0"N (4/3 and 5/7), 5/4 and 7+1 assigned as RGB. Each class has assumed to be with the same regolith 11°0'0"N characteristics. Input for regolith land unit mapping. 10°0'0"N 9°0'0"N Legend Class Name Class 5 Class 4 8°0'0"N Class 3 Class 2 Class 1 7°0'0"N 1:2,600,000 Kms 0 15 30 60 90 120 9/30/2016 Regolith Mapping 10
Results and Discussions Landform Map 35°0'0"E 36°0'0"E 37°0'0"E Output of slope and elevation classes overlay. 12°0'0"N · Input in regolith land units mapping process. Most of the study area is lowland 11°0'0"N Landform Slope% Elevation (m) Descriptions Foot slope 0-5 0-500 Lowest areas with flat slope 10°0'0"N Lowland 5-10 500-1000 Flat area with gentle slope Legend Landforms Plain 10-15 1000-1500 Broad, flat & rolling slope Footslope Hilltops Hilltops 15-30 1500-2000 Raised part with steep slope Lowland Mountains 9°0'0"N Mountains >30 >2000 High rock land with very steep Plain slope. Sources: Chabala et al. (2013); Worldlandforms.com. 8°0'0"N 7°0'0"N 1:2,600,000 0 15 30 60 90 120 Kms 9/30/2016 Regolith Mapping 11
Results and Discussions Regolith Land Unit Map Land units with relatively homogenous regolith character 35°0'0"E 36°0'0"E 37°0'0"E 12°0'0"N and similar landforms. · Each with specific slope and similar weathering intensity. But not necessarily show uniform regolith materials. 11°0'0"N Typically show associations where landform and regolith attributes are linked. 10°0'0"N The purity of the units depends on the mapping scale Legend Regolith Land Unit used. RLU1 9°0'0"N RLU2 RLU3 RLU4 RLU5 8°0'0"N 7°0'0"N 1:2,600,000 0 15 30 60 90 120 Kms 9/30/2016 Regolith Mapping 12
Conclusions The integrated Geospatial Technologies are found to be an indispensable approach in regolith mapping. Band ratio and DPCA techniques are vital in providing regolith and weathering information. Color compositing band ratio are effective in showing signatures of various regolith units. Despite the geology of the area is the same, five different units are identified. Revealed that degree of weathering is controlled by other factors like rainfall, vegetation and temperature in the study area. By accounting the effect of topography, five Regolith Land Units are also identified and mapped. Each RLUs could possibly show similar landform and regolith characteristics but the purity of the unit depends on the mapping scale. Generally, if supported by detail field data, the methodology followed in this research is effective in mapping regolith with time and cost effectively. 9/30/2016 Regolith Mapping 13
THANK YOU! 14 9/30/2016 Regolith Mapping
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